BrewTan B is *not* an "oxygen scavenging chemical". It may reduce protein (enzymatic) and metal ion based oxidative effects but not those caused by free oxygen in solution.
BrewTan B (BTB) *is* a tannic acid containing gallotannins. These gallotannins bind with certain proteins, specifically those from the proline and thiol groups - that participate in certain enzymatic oxidative reactions and reactions with heavy metals, and drop those proteins and metal ions out of solution. Chelating is the term used for bonding with metal ions.
Sulfites and Sulfides - including Sodium Metabisulfite (SMB), Sodium Sulfite, Sulfur Trioxide and Sulfur Dioxide *are* oxygen scavengers. They react with free oxygen in solution to produce various byproducts such as Sulfur Dioxide, various sulfates and sodium salts.
Ascorbic Acid (AA) *is* an oxygen scavenger but has the side effect of producing oxidative products (ions which cause further oxidation such as hydrogen peroxide) when it reacts with the free O2 in solution. It thus requires those oxidative products be reacted with some third party such as Sulfur Dioxide.
Hence you have the so-called "Trifecta" mixture of SMB/AA/BTB which happens to be made commercially in a product called "Antioxin SBT".http://www.lowoxygenbrewing.com/wp-content/uploads/2016/11/ANTIOXINSBT.pdf
Finding ones own ratios of each is the trick.
Basically your experiment tested the reduction or elimination of protein (enzymatic) and metal ion based oxidative reactions *not* the reduction or elimination of oxygen based oxidative reactions. It would be interesting to conduct three of these tests 1.) Eliminate or reduce the protein (enzymatic) and metal ion based oxidative reactions 2.) Eliminate or reduce the oxygen based oxidative reactions and 3.) Eliminate or reduce both protein (enzymatic) and metal ion - and oxygen based oxidative reactions.